Ag+-inducedenergylevelsplittinginLn-MOFsachievesenhancedEu3+emissionintensity<iclass="icon-zqcb"></i>

In lanthanide（Ln） complexes,the oversight of f-electrons and inner-shell relativistic interactions has constituted a critical gap,limiting a nuanced understanding and modulation of their luminescent properties.Addressing this issue,our study introduces a pioneering series of Ln-based metal-organic frameworks（Ln-MOFs）,designated as Ln-TCPP,utilizing tetraphenylpyrazinederived ligand and Ln3+ ions（Ln = Sm,Eu,Gd,Tb,Dy,Ho,Er,Tm,Yb and Lu） to modulate luminescence through advanced synthesis and theoretical analysis.We particularly emphasize the enhancement of Eu3+ luminescence in Ln-TCPP,where incorporating Ag+ ions to replace [（CH3）2NH2]+ within the Ln-MOFs plays a pivotal role.Theoretically,by employing timedependent density functional theory（TD-DFT） with full-electron relativistic effects,we demonstrate that Ag+ ions induce a splitting in the energy levels of Eu3+ .This splitting effectively reduces the rate of non-radiative transitions,significantly amplifying Eu3+ emission intensity.Our findings not only fill a long-standing void in understanding the all-electron relativistic interaction between f-electrons in Ln-MOFs luminescence but also establish a new strategy for controlling and optimizing the luminescent efficacy of these materials for potential applications.